[Surrogate markers in chronic kidney disease : Estimated glomerular filtration rate and albuminuria in clinical practice and in studies].

BACKGROUND

With decreasing estimated glomerular filtration rate (eGFR) and increasing albuminuria, the risk of cardiovascular events and overall mortality increases in chronic kidney disease (CKD). Established clinical renal endpoints often correspond to the late stage of CKD. Early stages are often initially asymptomatic.

OBJECTIVE

This article classifies the eGFR progression and changes in albuminuria as early markers and possible surrogate endpoints in CKD studies and describes key aspects for their clinical and methodological use in studies and benefit assessment.

RESULTS

The eGFR and the urine albumin-creatinine ratio (UACR) are complementary for risk stratification and progress monitoring, including in the cardiorenal context. Variability and influencing factors such as volume status, infections and blood pressure necessitate repeated measurements and contextual interpretation, especially in heart failure and after initiation of treatment with acute effects. For the eGFR Slope, a distinction is made between total Slope over several years and chronic Slope after the early acute phase. A meta-analysis of randomized studies reported a strong association between the total Slope averaged over 3 years and renal endpoints with a median R2 of 0.97, while the predictive accuracy of the chronic eGFR Slope was lower. Concerning albuminuria, it has been shown that higher UACR values are independently associated with cardiovascular mortality and that a reduction in UACR is associated with a more favorable renal prognosis.

CONCLUSION

The progression of the eGFR and albuminuria can improve the practicality of studies in early stages of CKD, lead to faster results and facilitate interdisciplinary classification if validation, time window, acute phase, standard treatment and competing risks are reported in a comprehensible manner.